Adjustable fixator

ABSTRACT

A bone fixator for securing a first bone portion in a position relative to second bone portion is disclosed, including at least two clamping assemblies each for receiving at least one bone pin and a main body disposed between the clamping assemblies. The main body includes at least one joint for orienting the clamping assemblies with respect to each other. The at least one joint may permit pivoting or rotation. Some joints permit the articulation of several components to be simultaneously and releasably lockable.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 10/265,258, filed Oct. 7, 2002, which claims the benefit of U.S.Provisional Application No. 60/327,294, filed Oct. 9, 2001, the entirecontents of both of which are expressly incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates generally to orthopaedic surgical devices,and more particularly to an adjustable fixator for securing bonesegments.

BACKGROUND OF THE INVENTION

Various types of orthopaedic devices are known for the fixation of bonefragments. Such devices typically are used to stabilize bones bymaintaining fractured bone portions in relatively fixed positions withrespect to each other. The alignment and stability provided by thedevices promotes the healing of fractures, allowing proper fusion tooccur.

Internal fixation devices include bone screws, which are used in avariety of orthopaedic applications for fixation of bone fragments. Bonefragments may be positioned in a desired configuration, and one or moreholes may be drilled and tapped across the fracture. Compression andstabilization of the bone fragments may then be effected by screwingbone screws into the holes. One limitation associated with bone screws,however, is that repositioning or adjusting the bone screws followingimplantation is difficult. In order to accommodate a differentalignment, it is often necessary to remove the original bone screws anddrill new holes for subsequent bone screw implantation.

Metal pins also are often used to stabilize bones. Similar to bonescrews, metal pins may be inserted in holes drilled across bonefragments to confer stability to the bone. However, as with bone screws,removal of the pins may be required if subsequent realignment of boneportions is necessary.

Intramedullary implants are another device used for fixation of bonefragments. Such a device may be placed in the central canal of afractured bone and locked thereto at the longitudinal ends of the deviceusing screws. The use of intramedullary implants is very invasive,though, and the implants are difficult to manipulate once installedwithin the canals of bone fragments.

External fixation devices also are commonly used to stabilize bonesegments. These devices employ a plurality of pins which extend througha patient's skin into holes drilled in fractured bone. Clamps are usedto secure the pins to a common apparatus, which may for example take theform of a rod that is disposed generally parallel to the anatomicallycorrect longitudinal axis of the fractured bone. The clamps incombination with the common apparatus create a rigid frame forimmobilizing the fracture to promote healing.

External skeletal fixation is a preferred method of treatment forvarious limb deformities, injuries, and other conditions including:severe open fractures, fractures associated with severe burns, fracturesrequiring distraction, fractures requiring limb lengthening,arthrodesis, infected fractures, and nonunions. External fixation offersseveral advantages over the above-mentioned internal fixationapproaches. For example, external fixation enables skeletalstabilization to be managed from a location that is generally remotefrom the proximity of deformity, injury, or disease, thereby permittingdirect surveillance of the limb and wound during related or subsequentprocedures. In addition, external fixation facilitates adjustment offracture alignment, bone lengthening, bone compression, and fixeddistraction following initial surgery. Furthermore, minimal interferencewith proximal and distal joints allows immediate mobilization of awounded limb, and insertion of the fixator pins can be performed underlocal anesthesia.

Despite these developments, there remains a need for fixation deviceswith improved adjustability. In particular, there remains a need forfixation devices with improved joints and overall constructions.

SUMMARY OF THE INVENTION

The invention relates to a bone fixator including at least two clampingassemblies each for receiving at least one bone fastener. The bonefixator includes a main body having first and second ends, a firstcoupling member, and a second coupling member. The first coupling membermay be pivotably coupled to the first end of the main body about a firstaxis, and the second coupling member may be pivotably coupled to thesecond end of the main body about a second axis. A wedge may be disposedwithin the main body, and may have a borehole disposed along atranslation axis. A locking member may be disposed along the translationaxis and may be operatively associated with the wedge. A first moveableelement may be disposed between the first coupling member and the wedge,and a second moveable element may be disposed between the secondcoupling member and the wedge. The wedge may be engageable with themoveable elements to arrest pivoting of the coupling members anddisengageable from the moveable elements to permit pivoting thereof withrespect to the main body. In some embodiments, the first and second axesmay be disposed transverse to each other, and in one embodiment, thefirst and second axes are disposed substantially perpendicular to eachother.

The borehole and locking member may be threadably associated with eachother. Further, the locking member may be fixed in position along thetranslation axis and rotatable thereabout. The moveable elements may beslidably associated with the wedge.

At least one of the coupling members and at least one of the lockingmembers may each have textured portions, with the textured portion ofthe at least one coupling member being positively lockable with thetextured portion of the at least one locking member. The texturedportions may include textures selected from serrations and facets. Atleast a portion of the main body may have an inner cylindrical surfaceand the moveable elements may be configured and dimensioned to beslidably associated with the cylindrical surface. The moveable elementsmay be resiliently biased toward each other.

The wedge may have first and second outer engagement surfaces disposedtransverse to each other. In some embodiments, the first and secondouter engagement surfaces are disposed at an angle of between about 10°and about 70°. In one embodiment, the first and second outer engagementsurfaces may be disposed at an angle of about 22°.

The moveable elements each may have an inner engagement surface, and theengagement surfaces of the moveable elements may be disposed at aboutthe same angle as the first and second outer engagement surfaces of thewedge.

At least one of the clamping assemblies may be operatively associatedwith the first coupling member. The at least one clamping assembly maybe translatable with respect to the first coupling member.

A distractor body may be operatively associated with the first couplingmember of the bone fixator, with at least one of the clamping assembliesbeing operatively associated with the distractor body. At least oneclamping assembly may be translatable with respect to the distractorbody and releasably lockable thereto. At least one of the clampingassemblies may include at least one of the first or second couplingmembers.

The bone fixator may further include a joint assembly having a jointassembly body with a borehole extending therethrough along a boreholeaxis and a fastener hole extending along a fastener axis transverse tothe borehole axis. The body may have an outer surface and an innerborehole surface. A slit may extend along the borehole axis and acrossthe fastener hole from the outer surface to the inner borehole surface,with the slit defining opposed slit surfaces having a separation width.The joint assembly also may include a fastener configured anddimensioned to be received in the fastener hole. The size of theborehole may be adjustable by changing the separation width of theopposed slit surfaces. The joint assembly body may further include atleast one rib disposed radially on the inner borehole surface, and thesecond coupling member may be retained in the joint assembly by the rib.In addition, a second rib may be provided on the joint assembly body,and a third coupling member may be retained in the joint assembly by thesecond rib.

The second and third coupling members may have opposed surfaces disposedin the borehole that are coupled together by an insert member. Theinsert member may extend within recessed portions of the second andthird coupling members. A link member may be disposed between the thirdcoupling member and a second of the clamping assemblies. The link membermay be pivotably associated with the second clamping assembly.

The slit of the joint assembly body may include first and secondsections, with the sections being oriented at an angle of between about20° and 50° with respect to each other. The joint assembly may be formedof a fiber-reinforced polymer.

The bone fixator may further include a second main body having a secondwedge, a second locking member, a third moveable element, and a fourthmoveable element.

The invention also relates to a bone fixator including at least twoclamping assemblies each for receiving at least one bone fastener. Thebone fixator may further include a main body disposed between theclamping assemblies, with the main body having a joint assembly. Thejoint assembly may include (1) a male segment having first and secondends and a projection extending from the second end, (2) a femalesegment having first and second ends, a cavity disposed proximate thefirst end and configured and dimensioned to receive at least a portionof the projection, and an opening connected to the cavity, and (3) acover piece configured and dimensioned to be received in the opening.When the male segment is inserted in the female segment and the coverpiece is disposed in the opening, the cover piece resists removal of theprojection and the male segment is releasably rotatable with respect tothe female segment.

The projection may include a serrated cylindrical portion and the coverpiece may include a serrated arcuate inner surface, with the serratedcylindrical portion and the serrated arcuate inner surface are mutuallypositively lockable. The female segment may further include a fastenerhole and the cover piece may further include a cover piece hole, withthe holes being coaxial when the cover piece is disposed in the opening.

The bone fixator also may include a fastener, so that when the fasteneris disposed in the coaxial fastener hole and cover piece hole, the coverpiece is securable to the female segment.

In addition, the bone fixator may include at least one tension clamp.The tension clamp may include a body having a borehole extendingtherethrough along a borehole axis and a fastener hole extending along afastener axis transverse to the borehole axis, with the body having anouter surface and an inner borehole surface. A slit may extend along theborehole and across the fastener hole from the outer surface to theinner borehole surface, with the slit defining opposed slit surfaceshaving a separation width. A fastener may be configured and dimensionedto be received in the fastener hole, and the size of the borehole may beadjustable by changing the separation width of the opposed slitsurfaces.

The present invention further relates to a bone fixator including atleast two clamping assemblies each for receiving at least one bonefastener, and a main body disposed between the clamping assemblies, withthe main body having at least one joint selected from the groupconsisting of: (1) a first joint including a main body having first andsecond ends, a first coupling member pivotably coupled to the first endand a second coupling member pivotably coupled to the second end, awedge disposed within the main body having a borehole disposed along atranslation axis, a locking member disposed along the translation axisand operatively associated with the wedge, a first moveable elementdisposed between the first coupling member and the wedge, a secondmoveable element disposed between the second coupling member and thewedge, with the wedge being engageable with the moveable elements toarrest pivoting of the coupling members and disengageable from themoveable elements to permit pivoting thereof with respect to the mainbody; (2) a second joint including a joint assembly body having an outersurface and a borehole extending therethrough along a borehole axisforming an inner borehole surface, and a fastener hole extending along afastener axis transverse to the borehole axis, a slit extendingsubstantially along the direction of the borehole and across thefastener hole from the outer surface to the inner borehole surface anddefining opposed slit surfaces having a separation width, with the sizeof the borehole being adjustable by changing the separation width of theopposed slit surfaces; and (3) a third joint including a male segmenthaving a projection extending from an end thereof, a female segmenthaving a cavity disposed proximate an end thereof and an openingconnected to the cavity, the cavity being configured and dimensioned toreceive at least a portion of the projection, and a cover piececonfigured and dimensioned to be received in the opening, wherein whenthe male segment is inserted in the female segment and the cover pieceis disposed in the opening, the cover piece resists removal of theprojection and the male segment is releasably rotatable with respect tothe female segment. The main body of the bone fixator may include atleast two different joints selected from the first joint, the secondjoint, and the third joint. In one embodiment, the main body comprisesat least one first joint and at least one second joint.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred features of the present invention are disclosed in theaccompanying drawings, wherein similar reference characters denotesimilar elements throughout the several views, and wherein:

FIG. 1 shows an exploded view of one embodiment of an apparatus for theexternal fixation of bones;

FIG. 2 shows an exploded view of the distractor body of FIG. 1;

FIG. 2A shows a side view at one end of the distractor body of FIG. 2;

FIG. 2B shows a cross-sectional view of the distractor body of FIG. 2intermediate to the ends of the body;

FIG. 2C shows a cross-sectional view of the distractor body of FIG. 2along line IIC-IIC;

FIG. 2D shows a lock piece of FIG. 1;

FIG. 2E shows a lock bar of FIG. 1;

FIG. 2F shows another lock piece of FIG. 1;

FIG. 2G shows a lock screw of FIG. 1;

FIG. 3 shows an exploded view of the distractor clamp assembly of FIG.1;

FIG. 4A shows a side view of the distractor bar of FIG. 1;

FIGS. 4B and 4C show cross-sectional views of the distractor bar of FIG.4A along line IVB-IVB and IVC-IVC, respectively;

FIG. 5 shows an exploded perspective view of the first body portion ofFIG. 1;

FIG. 5A shows an assembled perspective view of the first body portion ofFIG. 5;

FIGS. 5B-5C show partial cross-sectional perspective views of the firstbody portion of FIG. 5 without o-rings being shown;

FIG. 5D shows a side view of a first lock piece of FIG. 1;

FIG. 5E shows a cross-sectional view along line VE-VE of a first lockpiece of FIG. 1;

FIG. 5F shows a side view of a second lock piece of FIG. 1;

FIG. 5G shows a cross-sectional view along line VG-VG of a second lockpiece of FIG. 1;

FIG. 5H shows a side view of the wedge actuator of FIG. 5;

FIG. 5I shows a bottom view of the wedge actuator of FIG. 5;

FIG. 5J shows a top view of the wedge actuator of FIG. 5;

FIG. 5K shows a front view of the wedge actuator of FIG. 5;

FIG. 5L shows a cross-sectional view along line VL-VL of the wedgeactuator of FIG. 5H;

FIG. 5M shows a side view of the joint lock screw of FIG. 1;

FIG. 5N shows a side view of the body joint of distractor joint assemblyof FIG. 1;

FIG. 5O shows a cross-sectional view of the body joint of distractorjoint assembly of FIG. 5N along line VO-VO;

FIG. 5P shows another side view of the body joint of distractor jointassembly of FIG. 5N;

FIG. 5Q shows a cross-sectional view of the body joint of distractorjoint assembly of FIG. 5I) along line VQ-VQ;

FIG. 6A shows a side view of the joint of the central clamp assembly ofFIG. 1;

FIGS. 6B and 6C show cross-sectional views of the joint of the centralclamp assembly of FIG. 6A along line VIB-VIB and VIC-VIC, respectively;

FIG. 7A shows a side view of the coupling of FIG. 1;

FIG. 7B shows a cross-sectional view of the coupling of FIG. 7A alongline VIIB-VIIB;

FIG. 7C shows a cross-sectional view of the coupling of FIG. 7A alongline VIIC-VIIC;

FIG. 8A shows the central clamp assembly of FIG. 6A with a pair ofcouplings inserted therein;

FIG. 8B shows a cross-sectional view of the assembled central clampassembly of FIG. 8A along line VIIIB-VIIIB;

FIG. 8C shows an exploded perspective view of the assembled centralclamp assembly of FIG. 8A;

FIG. 9A shows an exploded perspective view of the second body portion ofFIG. 1;

FIG. 9B shows an assembled perspective view of the second body portionof FIG. 9A;

FIG. 9C shows a cross-sectional view of the T-clamp link of FIG. 9A;

FIG. 10A shows an exploded perspective view of the T-clamp assembly ofFIG. 1;

FIG. 10B shows a top view of the T-clamp pivot of FIG. 1;

FIG. 10C shows a side view of the T-clamp pivot of FIG. 10B;

FIG. 10D shows a cross-sectional view along line XD-XD of the T-clamppivot of FIG. 10B;

FIG. 11 shows an exploded view of another embodiment of a joint assemblyfor use with an apparatus for the external fixation of bones;

FIG. 12A shows a perspective view of a tension clamp of FIG. 11;

FIG. 12B shows a side view of the tension clamp of FIG. 12A;

FIG. 12C shows a cross-sectional view along line XIIC-XIIC of thetension clamp of FIG. 12A;

FIG. 12D shows the direction of fiber reinforcement of the tension clampof FIG. 12A;

FIG. 12E shows a cross-sectional view of the tension clamp of FIG. 12Calong line XIIE-XIIE;

FIG. 12F shows a top view of the tension clamp of FIG. 12A;

FIG. 12G shows a perspective view of a insert nut of FIG. 11;

FIG. 12H shows a top view of the first rotatable segment of FIG. 11;

FIG. 12I shows a cross-sectional view of the first rotatable segment ofFIG. 12H along line XII I-XII I;

FIG. 12J shows a cross sectional view of the rotatable segment cap ofFIG. 11 along a central longitudinal plane;

FIG. 13A shows a bottom view of the main body of FIG. 11;

FIG. 13B shows a cross-sectional view of the main body of FIG. 13A alongline XIIIB-XIIIB;

FIG. 13C shows a top view of the main body of FIG. 13A;

FIG. 13D shows a bottom view of the cover of FIG. 11; and

FIG. 13E shows a cross-sectional view of the cover of FIG. 13D alongline XIIIE-XIIIE.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring initially to FIG. 1, an adjustable fixator 10 according to oneembodiment of the present invention is shown. Fixator 10 is suitable forstabilizing and rigidly fixing bone fragments or segments with respectto each other, and may be made of any suitable material such astitanium, stainless steel, polymers, alloys, composites, or othermaterials. Fixator 10 includes a distractor body 12 and associateddistractor clamp assembly 14, as well as a first body portion 16 with adistractor bar 18, distractor joint assembly 20, and coupling 22.Distractor body 12 and associated components may be used for distractionand compression. In addition, fixator 10 includes a central jointassembly 24, along with a second body portion 26 having a coupling 28, aT-clamp joint assembly 30, and a T-clamp link 32. A T-clamp assembly 34is preferably secured to a T-clamp pivot 36 that is pivotably associatedwith T-clamp link 32.

Turning to FIGS. 2 and 2A-2C, distractor body 12 includes a centralthrough-hole 38 extending along an axis 39 from first end 40 to secondend 42. A distractor screw 44 with at least a partially threaded body 45is disposed about axis 39 and received in through-hole 38. Distractorscrew 44 is rotatably associated with first end 40 of distractor body 12using a distractor screw collar 46 that may be pinned to distractorscrew 44 as with a dowel pin 19. Preferably, dowel pin 19 rigidly fixesdistractor screw collar 46 to distractor screw 44 such that rotation ofscrew 44 rotates collar 46. Distractor body 12 includes a stop 48against which bears shoulder 50 of screw 44. Head 52 a of screw 44extends within first end 40, and is received in collar 46. Preferably,head 52 a includes a hexagonal or other shaped recessed region that maybe engaged by a suitably shaped tool, such as a hexagonal key. Thus,with head 54 bearing against first end 40, and shoulder 50 bearingagainst stop 48, screw 44 may be turned about axis 39 while remaining ina longitudinally fixed position with respect to distractor body 12.

As shown in FIG. 3, distractor clamp assembly 14 includes opposing frontand rear vise plates 56, 58, respectively each having grooves 59 forreceiving bone fasteners. Plates 56, 58 are aligned with distractor lockscrew 60, the head 62 of which preferably may be slidably received incentral through-hole 64 a of front vise plate 56, and the shank 64 b ofwhich preferably may be threadably received in distractor nut 66. Viseplates 56, 58 are additionally coupled together with a pair of visescrews 68 each having a vise washer 70. Vise screws 68 extend throughholes 72, 74, within respective compression springs 76, and preferablymay be threadably received in holes 78, 80 in rear vise plate 58. Thus,it should be noted that until vise plates 56, 58 of distractor clampassembly 14 are tightened with respect to each other, springs 76 biasvise plates 56, 58 away from each other while permitting vise plates 56,58 generally to be disposed in either parallel or non-parallel planes asa function of the degree of tightening of each vise screw 68. The upperand lower ends of springs 76 also may abut recessed regions in viseplates 56, 58. Compression springs 76 preferably may be formed ofstainless steel and have a spring rate of about 0.16 kg/mm. Thedistractor clamp assembly 14 receives bone fasteners, for example bonepins or bone screws, which are inserted into bone.

Distractor clamp assembly 14 is demountably coupled to distractor body12 by inserting rail portion 82 in groove 84 of distractor body 12. Asshown particularly in FIGS. 2A and 2B, groove 84 has a maximum width L₁at first end 40, while along the remainder of distractor body 12, groove84 has a maximum width L₂ that is greater than length L₁. Preferably,distractor nut 66, which abuts rear vise plate 58, rides in groove 84 onflat face 86 so that the travel of plate 58 is arrested when distractornut 66 reaches first end 40. Because length L₃ of distractor nut 66 isgreater than length L₁ of groove 84 at first end 40, distractor clampassembly 14 is prevented from uncoupling by sliding in the direction offirst end 40. Moreover, movement of distractor clamp assembly 14 withrespect to distractor body 12 is permitted because length L₃ ofdistractor nut 66 is about the same as length L₂ of groove 84 indistractor body 12. In addition, rail portion 82 preferably may be sizedto be slidably received in groove 84 while abutting upper faces 88, 90of groove 84. Faces 88, 90 are disposed in transverse planes such thatrail portion 82 is retained in groove 84. To fix the position ofdistractor clamp assembly 14, distractor lock screw 60 is tightened tobring distractor nut 66 firmly against overhangs 92, 94 of groove 84 indistractor body 12. Distractor nut 66 may include an oblong projection66 a proximate the threaded hole therein, with projection 66 a beingconfigured and dimensioned to mate within a like-shaped recess in rearvise plate 58 to thereby prevent rotation of distractor nut 66 withrespect to rear vise plate 58.

As shown in FIGS. 1, 2 and 2C, distractor body 12 is preferably providedwith a through-slot 96 in which are disposed opposing lock pieces 98,100 with a lock bar 102 positioned therebetween. A threaded distractorlock screw 104 is received in lock piece 100 and threadably received inlock piece 98, so that once lock pieces 98, 100 and lock bar 102 aredrawn toward and abut each other, the travel of distractor clampassembly 14 may be arrested when distractor nut 66 comes in contacttherewith. These components are shown in detail in FIGS. 2D-2G.

Turning now to FIGS. 4A-4C, distractor bar 18 is shown with a generallyflat end 106, a body portion 107, a generally arcuate, serrated portion108, and a through-hole 109. Preferably, serrations on serrated portion108 are disposed about a circular path of about 180°. A through-slot 110is disposed in body 107 proximate flat end 106, and receives a threadeddistractor nut 112, as shown in FIG. 1. Distractor bar 18 is disposedabout a distractor axis 114, and when axis 114 coincides with axis 116of adjustable fixator 10, end 106 may be inserted into blind hole 38 ofdistractor body 12. The cross-section of body portion 107 of distractorbar 18 is keyed, as shown in FIG. 4C, with an arcuate section 118 and aflat section 120. Blind hole 38 of distractor body 12 serves as a keywayfor receiving body portion 107. Thus, one preferred orientation ofdistractor bar 18 may be set with respect to distractor body 12 as wellas distractor clamp assembly 14. It can be appreciated that the keywayand through-hole may take other shapes to provide a desired orientation,to prevent rotation, or both.

A hole 122 is provided in distractor bar 18, and is disposed centrallyabout distractor axis 114. Hole 122 is sized to receive threaded body 45of distractor screw 44. Preferably, threaded body 45 is threadablyassociated with threaded distractor nut 112. Alternatively, or inaddition thereto, threading may be provided in hole 122 of distractorbar 18. Thus, because distractor screw 44 is held in a fixed positionwith respect to distractor body 12, turning of distractor screw 44 aboutcoincident axes 39, 114, 116 results in either an increase or decreasein the overall length of an assembled distractor body 12 and distractorbar 18. Such length adjustments thus permit distraction or compressionof bone segments to be achieved using fixator 10. Desired lengthadjustments may be measured, for example, using a scale 124 provided ona side of distractor bar 18, for example a flat 126 a, as shown in FIGS.1 and 4C.

Referring to FIG. 2, in order to prevent over-extension of distractorscrew 44 and inadvertent disassembly, an unthreaded gap 45 a may beprovided along threaded body 45 near threaded end portion 52 b. In oneexemplary embodiment, a gap 45 a larger than the width of distractor nut112 and sized to about 5 mm is provided, in which region the diameter ofbody 45 is smaller than at threaded regions. Further translation ofdistractor screw 44 with respect to distractor nut 112 thus can beavoided when gap 45 a reaches distractor nut 112. Because unthreaded gap45 a is not disposed at a free end of distractor screw 44, travel ofdistractor body 12 with respect to distractor body 18 may be interruptedyet distractor body 12 does not become detached from distractor body 18.

Referring to FIGS. 5-5C, and as discussed earlier with respect to FIG.1, first body portion 16 includes a distractor bar 18, distractor jointassembly 20, and coupling 22 with integral serrated portion 125. Thesecomponents are shown aligned with axes 39, 114, 116. Joint assembly 20is configured to permit swivelling or articulation of distractor bar 18and coupling 22 about generally perpendicular axes 126, 128,respectively. In addition, joint assembly 20 is configured to permitreleasable locking of such articulation of distractor bar 18 andcoupling 22, simultaneously, using joint lock screw 129 as will beexplained below. Thus, releasable locking may be achieved simultaneouslyin two degrees of freedom. To this end, housed in joint assembly body 20a of joint assembly 20 are a first lock piece 130, a wedge actuator 132,and a second lock piece 134, an exemplary assembled configuration ofwhich is shown in partial cross-section in FIGS. 5B-5C.

A side view of first lock piece 130 is shown in FIG. 5D, while across-section is shown in FIG. 5E. Similarly, side and cross-sectionalviews of second lock piece 134 are shown in FIGS. 5F and 5G. As evidentfrom the side views of FIGS. 5D and 5F, lock pieces 130, 134 havearcuate side walls 131, 135, respectively. In one exemplary embodiment,lock piece 130 has two arcuate recesses 136 on side wall 131, while lockpiece 134 has two arcuate recesses 138 on side wall 135. As shown inFIGS. 5 and 5C, each pair of opposed recesses 136, 138 is sized toreceive a resilient o-ring 139, which seats in the recesses and provideslimited biasing of lock pieces 130, 134 toward each other. In analternate embodiment, a tension spring could be used in place of o-ring139. Preferably, upper recesses 140, 142 are provided in lock pieces130, 134, respectively, to receive a portion of joint lock screw 129,just below the head thereof. Serrated portion 108 of distractor bar 18engages serrated portion 144 of first lock piece 130, while serratedportion 125 of coupling 22 engages serrated portion 146 of second lockpiece 134.

Lock pieces 130, 134 are configured to slidingly engage wedge actuator132. In an exemplary embodiment, inner surfaces 148, 150 of lock pieces130, 134 are disposed in transverse planes at an angle of about 22° withrespect to each other. As shown in FIGS. 5E and 5G, inner surface 148preferably may be oriented at an angle θ₁ with respect to a lineperpendicular to bottom face 149 of first lock piece 130, and innersurface 150 preferably may be oriented at an angle θ₂ with respect to aline perpendicular to bottom face 151 of second lock piece 134. Anglesθ₁,θ₂ are preferably about the same, each preferably between about 5°and about 35°, and more preferably about 11°. Inner surfaces 148, 150serve as contact surfaces upon which wedge actuator 132 slides. Turningto FIGS. 5H-5L, wedge actuator 132 includes a pair of outer surfaces152, 154 disposed in transverse planes, such that outer surfaces 152,154 are disposed at an angle θ₃ with respect to each other. Preferably,angle θ₃ is about twice the amount of angles θ₁ or θ₂, and between about10° and about 70°, and more preferably about 22°. Inner surfaces 148,150 of lock pieces 130, 134 may each slidingly engage one of the outercontact surfaces 132 a, 132 b of wedge actuator 132.

The position of wedge actuator 132 between first and second lock pieces130, 134 is adjustable using joint lock screw 129, shown in FIG. 5M.Joint lock screw 129 has a head 156 and a threaded shaft 158.Preferably, head 156 includes a hexagonal or other shaped region thatmay be engaged by a suitably shaped tool, such as a hexagonal key.Preferably, the shaped region is recessed but the outer surface of thehead 156 may itself be shaped to engage a tool. Shaft 158 preferablythreadably engages a threaded hole 160 in wedge actuator 132. When fullyassembled, head 156 preferably abuts a washer 162 that rests in acorresponding recess 164 in joint assembly body 20 a of joint assembly20. Lower portion 166 of joint lock screw 129 protrudes from an oppositeside of joint assembly body 20 a, and is fixed in place by a cap 168.Lower portion 166 of joint lock screw 129 includes a through hole 166 adisposed transverse to the longitudinal axis of shaft 158, and cap 168similarly includes a through hole 168 a so that when cap 168 is disposedon joint lock screw 129, through hole 166 a may be aligned with throughhole 168 a. Once aligned, a pin 168 b may be inserted therein,preferably with an interference fit, to couple cap 168 and joint lockscrew 129. In an alternate embodiment, lock screw 129 is fixed in placeby a retaining ring coupled to lower portion 166 at a groove therein.Optionally, a washer 168′ may be provided between the retaining ring andjoint assembly body 20 a (shown for example in FIGS. 5B and 5C).

An exemplary embodiment of joint assembly body 20 a of joint assembly 20is shown in FIGS. 5N-5Q. As shown in FIG. 50, joint assembly body 20 apreferably has a generally circular cross-section, adapted to receivelock pieces 130, 134 with similar arcuate outer walls. Referring againto FIG. 5A, lock pieces 130, 134 are retained within joint assembly 20using joint pivot pins 170, 172. Pin 170 couples distractor bar 18 tojoint assembly body 20 a, and is received in coaxial holes 174 of jointassembly body 20 a and through-hole 109 of distractor bar 18. Similarly,pin 172 couples the coupling 22 to joint assembly body 20 a, and isreceived in coaxial holes 176 of joint assembly body 20 a andthrough-hole 178 of coupling 22.

In operation, joint lock screw 129 preferably may be threadablyassociated with threaded hole 160 in wedge actuator 132. Because lockscrew 129 is positionally fixed by cap 168, although rotatable about itscentral axis 180, threadable engagement of lock screw 129 with wedgeactuator 132 results in upward or downward travel of wedge actuator 132with respect to head 156 of lock screw 129, along central axis 180.During upward movement, outer contact surface 132 a of wedge actuator132 slidingly engages inner surface 148 of lock piece 130, and outercontact surface 132 b of wedge actuator 132 slidingly engages innersurface 150 of lock piece 134, so that serrated portions 144, 146 oflock pieces 130, 134 are engaged with serrated portion 108 of distractorbar 18 and serrated portion 125 of coupling 22 to releasably lock thecomponents in place. Thus, the angulation of distractor bar 18 aboutaxis 126 as well as the angulation of coupling 22 about axis 128 may bereleasably fixed. Downward movement of wedge actuator 132 simultaneouslyreleases pressure between the mutually engaging serrated surfaces oflock pieces 130, 134, distractor bar 18, and coupling 22, so thatdistractor bar 18 and coupling 20 of fixator 10 may be readily angulatedwith respect to each other.

While the embodiment shown and described herein has the ability to lockrotation or articulation of components about generally perpendicularaxes, in other embodiments the axes need not be perpendicular. Forexample, a wedge actuator 132 may be disposed between a pair of lockpieces 130, so that the serrations of the lock pieces and the directionof articulation are about the same on either side of wedge actuator 132.Alternatively, a pair of lock pieces 134 may be used. Thus, the pair ofcomponents such as distractor bar 18 and coupling 22 may be orientedwithin the same plane. In yet other embodiments, the axes definingarticulation of the two components may be transverse to each other, sothat the components may be oriented in transverse planes.

Referring next to FIGS. 1 and 6A-6C, central joint assembly 24 is shownhaving a joint 24 a with a borehole 182 extending therethrough along aborehole axis 184. Borehole 182 is configured and dimensioned forreceiving opposing couplings 22, 28, as will be described shortly. Inone exemplary embodiment, joint 24 a of central joint assembly 24includes a slit 186 from side surface 188 to borehole surface 190, andwhich extends the length of joint 24 a to define assembly portions 192,194. A fastener hole 196 is also included, and extends from side surface198 to side surface 199, through assembly portions 192, 194. A threadedcenter clamp screw 200, preferably seated on a spherical washer 202,extends through fastener hole 196, and threadably engages a stainlesssteel threading insert 204 disposed in fastener hole 196 proximate sidesurface 198. Spherical washer 202 preferably is seated in a sphericalrecess in joint 24 a of central clamp assembly 24 proximate side surface199. The spherical geometry of the washer and recess aid in the clampingaction of center clamp screw 200. In an alternate embodiment, fastenerhole 196 may be threaded between connecting assembly portion 194 andside surface 198.

As shown particularly in FIG. 6B, borehole 182 of joint 24 a of centraljoint assembly 24 is generally symmetrical about a plane through centeraxis 206, which plane is perpendicular to borehole axis 184. Borehole182 generally has an inner diameter D₁, but includes circumferentialinner ribs 208, 210 which form an inner diameter D₂ that is smaller thandiameter D_(I).

Couplings 22, 28 are configured and dimensioned to be received inborehole 182 and releasably rotate therein. Turning to FIGS. 7A-7C, eachcoupling 22, 28 includes an integral serrated portion 125 and a flatface 212. A circumferential groove 214 is sized to receive one of theribs 208, 210 in borehole 182 and rotate about borehole axis 184.Alternatively, one of the couplings 22, 28 may be formed with a recess216 and the other coupling may be formed with a projection which fitsinto and corresponds with recess 216. In addition, a hollow portion 216may be provided. In some embodiments, as shown in FIGS. 8A-8C, a centralsupport piece 218 is disposed in hollow portions 216 between couplings22, 28 to provide increased stiffness along borehole axis 184. In oneexemplary embodiment, one coupling 22, 28 may be retained in borehole182 with a set screw or pin 220, which extends through a hole 222 injoint 24 a of central joint assembly 24 and is received in a recess 224in the coupling 22, 28. The set screw or pin 220 may permit one coupling22, 28 to be rotationally fixed with respect to central joint assembly24, while the other coupling 22, 28 may freely rotate. Thus, access tocenter clamp screw 200 may be permitted while a coupling 22, 28 isrotated. When slit 186 is generally open, as shown for example in FIG.6C, couplings 22, 28 are free to slidably rotate in borehole 182. When adesired orientation of couplings 22, 28 has been chosen about rotationalaxis 184, screw 200 may be tightened, thereby decreasing the separationof regions 192, 194 of joint 24 a and arresting rotation of couplings22, 28. Preferably, the rotation of each coupling 22, 28 issimultaneously governed by the degree of tightening of screw 200; thus,both couplings 22, 28 either are free to rotate or fixed in position.

In an alternate embodiment, borehole 182 of joint 24 a of central jointassembly 24 may be smooth, without inner ribs 208, 210. A pair of setscrews or pins 220 may be received in suitable holes in central jointassembly 24. One screw or pin 220 may be received in a recess 224 ineach coupling 22, 28 such that couplings 22, 28 may be retained inborehole 182.

As shown in FIGS. 9A to 9C, second body portion 26 includes a coupling28, a T-clamp joint assembly 30, and a T-clamp link 32. T-clamp jointassembly 30 of second body portion 26 is the same as distractor jointassembly 20, which was previously described with respect to FIGS. 5B to5Q, and thus is not described again in detail. However, it should benoted that second body portion 26 is configured to permit swivelling orarticulation of coupling 28 and T-clamp link 32 about generallyperpendicular axes 226, 228, respectively. When second body portion 26is aligned about axis 116 of adjustable fixator 10, as shown for examplein FIG. 1, axis 226 is parallel to axis 126 of distractor joint assembly20, while axis 228 is parallel to axis 128 of assembly 20. However,these axes may be non-parallel as a result of the articulation permittedby first body portion 16, central joint assembly 24, and second bodyportion 26.

With reference to FIGS. 9A to 9C, T-clamp link 32 is provided withserrations on a serrated portion 230 that are disposed about a circularpath of about 180°. Serrated portion 230 of T-clamp link 32 engages withserrated portion 146 of lock piece 134 so that T-clamp link 32 may bereleasably locked in place. A pin 172 couples T-clamp link 32 to jointassembly body 20 a of T-clamp joint assembly 30, and is received incoaxial holes 176 of joint assembly body 20 a and a through-hole 232 oflink 32. T-clamp link 32 is further provided with a body portion 234 anda pair of extensions 236, 238 with coaxial holes 240 disposed on an axis242. Preferably, axes 228, 242 are parallel. Extensions 236, 238 definea central opening 244 that preferably is disposed symmetrically aboutlink central axis 246, and is sized to accommodate T-clamp pivot 36 aswill be described. A pair of pin holes 248, 250 are also provided inextensions 236, 238, and are preferably disposed perpendicular to hole240. As shown in FIG. 1, a T-clamp pivot pin 252 is inserted in holes240, and secured to extensions 236, 238 by cross pins 254 that fit inpin holes 248, 250 as well as like positioned holes in pivot pin 252. Aninterference fit may be used between portions of cross pins 254 and pinholes 248, 250 to retain cross pins 254 therein. Preferably, T-clamppivot pin 252 is rotationally fixed with respect to T-clamp link 32.

Turning to FIG. 10A, T-clamp assembly 34 is shown with opposing frontvise plate 256 and rear vise plate 258 each having grooves 259 forreceiving bone fasteners. Plates 256, 258 are connected with a T-clamplock screw 260, as shown in FIG. 1. Lock screw 260 projects throughholes 280, 282 in plates 256, 258, respectively, which are coupledtogether with a pair of vise screws 68 each having a vise washer 70.Vise screws 68 extend through holes 262, 264, within respectivecompression springs 76, and preferably may be threadably received inholes 266, 268 in rear vise plate 258. Thus, it should be noted thatuntil vise plates 256, 258 of T-clamp assembly 34 are tightened withrespect to each other, springs 76 bias vise plates 256, 258 away fromeach other while permitting vise plates 256, 258 generally to bedisposed in either parallel or non-parallel planes as a function of thedegree of tightening of each vise screw 68. The upper and lower ends ofsprings 76 also may abut recessed regions in vise plates 256, 258. Rearvise plate 258 also is provided with a pair of holes 270, 272 throughwhich clamp attachment screws 274 a extend. As shown in FIGS. 1 and 10Bto 10D, T-clamp pivot 36 includes a pair of outer holes 274, 276 whichare disposed such that attachment screws 274 a may be received therein.A central hole 278 in T-clamp pivot 36 may be disposed coaxially withholes 280, 282 in vise plates 256, 258, respectively, and holes 278,280, 282 receive T-clamp lock screw 260. Lastly, a through hole 284 isdisposed in extension 286 of T-clamp pivot 36, and preferably runsperpendicular to hole 278. The hole 278 includes a threaded portion 278a and an unthreaded counterbore portion 278 b, with the diameter ofcounterbore 278 b being larger than the diameter of threaded portion 278a.

T-clamp pivot 36 is coupled to T-clamp link 32 when T-clamp pivot pin252 extends through coaxial holes 240, 284. A hexagonal or other shapedregion, preferably a recessed region, may be provided in upper end 260 aof lock screw 260, and may be engaged by a suitably shaped tool, such asa hexagonal key. Lock screw 260 preferably has a threaded shank 260 bwhich is threadably associated with threaded portion 278 a of hole 278in T-clamp pivot 36. To arrest pivoting of T-clamp assembly 34 aboutT-clamp pivot pin 252, in one exemplary embodiment, T-clamp lock screw260 may be positioned so that lower end 260 c of T-clamp lock screw 260bears against T-clamp pivot pin 252. The body of T-clamp pivot pin 252may be generally hexagonal such that flats are included along the bodyto provide more surface area for lower end 260 c of T-clamp lock screw260 to bear against. Lower end 260 c of T-clamp lock screw 260 (shown inFIG. 1) forms a shoulder that abuts the shoulder formed at theintersection of portions 278 a, 278 b of hole 278 in T-clamp pivot 36(shown in FIG. 10D), thereby limiting travel of T-clamp lock screw 260.

Other embodiments of clamp assembly 14 and/or T-clamp assembly 34 alsomay be employed. For example, T-clamp pivot 36 may be integrally formedwith lower vise plate 258, obviating the need for attachment screws 274a extending through holes 270, 272.

In an exemplary embodiment, distractor body 12, distractor bar 18,couplings 22, 28, T-clamp link 32, and lock pieces 130, 134 are formedof a polymer such as Victrex® 450CA30, a radiolucent carbon fiberreinforced polyaryletherketone thermoplastic which can withstand manyautoclave sterilization cycles and concomitantly possesses highmechanical strength, resistance to stress cracking, as well as chemicalresistance. The radiolucent properties of this polymer advantageouslypermit visualization of underlying bones and/or joints when fixator 10is disposed in the field of view of x-ray equipment, thus for examplepermitting imaging of the anatomic alignment of bones and/or thesurfaces of joints proximate the fixator. This polymer also is chosenfor its relatively light weight. Preferably, T-clamp link 32 is formedof a radiolucent polymer so that shadows are avoided in imaging.Advantageously, when the fixator of the present invention is used inconnection with the treatment of badly comminuted distal tibiafractures, otherwise known as pilon fractures, the radiolucent T-clamplink permits suitable joint visualization.

Preferably, body joints 20 a of distractor joint assembly 20 and T-clampjoint assembly 30, as well as joint 24 a of central joint assembly 24,are formed of 6061-T6 aluminum, which provides radiolucentcharacteristics when suitably thin. Vise plates 56, 58, 256, 258 andT-clamp pivot 36 are formed of titanium alloy (Ti-6% Al-4% V), and wedgeactuator 132 is preferably formed of 17-4 PH hardened stainless steel.In an alternate embodiment, wedge actuator 132 is formed of 316Lstainless steel. Other fasteners or fastener-like components disclosedherein, such as joint lock screw 129, preferably may be metallic and maybe formed of a material of suitable hardness such as 17-4 PH hardenedstainless steel or 316L stainless steel. Fasteners may also be providedwith a surface coating of electroless nickel with phosphorous that isco-deposited with polytetrafluoroethylene (PTFE), as available forexample from Anoplate Corporation, Syracuse, N.Y. Such a surface coatingprovides resistance to galling, and also provides lubrication.Alternatively, the fasteners or fastener-like components may be formedof a material that resists galling such as gall tough stainless steel.

Thus, to summarize the articulation provided by adjustable fixator 10,distractor joint assembly 20 permits angulation of components about twopreferably perpendicular axes, central joint assembly 24 permitsrotation of components about two preferably parallel planes, T-clampjoint assembly 30 permits angulation of components about two preferablyperpendicular axes, and T-clamp pivot 36 permits angulation about anadditional axis. Furthermore, the overall length of adjustable fixator10 may be grossly adjusted, and the position of distractor clampassembly 14 may be adjusted relative to distractor body 12. Fine lengthadjustments, for example to achieve compression and distraction, may beaccomplished using distractor screw 44.

Turning now to FIG. 11, an alternate arrangement of joints is shown foruse in an external fixator. Joint assembly 300 includes a distractor rod302, a first rotatable segment 304, a rotatable segment cap or swivelsegment 306, a second rotatable segment 308, and a T-clamp link 310.Clamp assemblies suitable for holding bone pins may be secured at eitherend of joint assembly 300. A tension clamp 312 couples distractor rod302 to first rotatable segment 304, and another tension clamp 314couples second rotatable segment 308 to T-clamp link 310. As shown inFIG. 11, tension clamps 312, 314 are mirror images of each other. Thus,while tension clamp 312 will be discussed in detail, the discussionapplies to tension clamp 314 as well.

Referring to FIGS. 12A to 12F, tension clamp 312 includes a generallycylindrical body portion 315 with a first through hole 316 disposedalong a first central hole axis 318. A pair of generally parallelextensions 319 a, 319 b are connected to body portion 315, and include asecond through hole 320 that is disposed along a second central holeaxis 322. Preferably axes 318, 322 are generally perpendicular to eachother. Extensions 319 a, 319 b are biased apart, separated by a slit 324which extends from side surfaces 326 to through hole surface 328 and thewidth of tension clamp 312. Slit 324 preferably includes first andsecond sections 329 a, 329 b, respectively, that are oriented at anangle α with respect to each other. In one exemplary embodiment, angle αis between about 20° and 50°, and more preferably about 33.6°. As shownin FIG. 12D, fiber reinforcement preferably may be provided along thedirection of arrows A. Preferably, as shown in FIG. 11, an insert nut330 a may be seated in through hole 320 and receives a fastener 332 witha smooth upper portion 332 a and threaded lower portion 332 b. Eachfastener 332 preferably includes a head with a spherical lower portionfor mating in a spherical recess. In one embodiment shown in FIG. 12G,insert nut 330 a has a circular head 334, a non-circular body 336, and acentral through-hole 337. Non-circular body 336, for example, may besquare-shaped or any other suitable shape. Preferably, the seat inthrough-hole 320 has a similarly non-circular shape so that insert nut330 a does not freely rotate therein. Insert nut 330 a additionally maybe adhesively bonded to body 336.

First rotatable segment 304 is provided with a through hole 340 intowhich opposing insert nuts 330 b and 330 c are seated. Preferably, asdescribed with respect to insert nut 330 a, seats in through hole 340are shaped so that when insert nuts 330 b,330 c are inserted therein,rotation is prevented. Preferably, the upper surface 338 of head 334 ofinsert nuts 334 a,334 b is serrated, such as with a star-grind pattern,so that when the heads 334 of insert nuts 334 a,334 b abut each other,the serrated surfaces on the heads frictionally mate and may rotate withrespect to each other about substantially regularly spaced engagingserrations.

Thus, when heads 334 of opposing insert nuts 334 a,334 b are looselydisposed with respect to each other, the heads are free to rotate withrespect to each other, whereas when heads 334 are pressed firmly againsteach other, rotational movement is arrested. First rotatable segment 304further may include a recessed region 342, so that when the body 336 ofan insert nut 330 b is disposed in hole 340, head 334 substantially fitswithin recessed region 342. In an exemplary embodiment, the through-hole337 in insert nuts 330 a,330 b is smooth, while through-holes 337 ininsert nuts 330 c are threaded to receive threaded lower portions 332 bof fasteners 332.

When assembled, a yoke pin 339 is received in coaxial holes 316, 341 a,341 b of distractor rod 302. In an exemplary embodiment, yoke pin 339 iskeyed so that it does not rotate with respect to distractor rod 302.Thus, a tension clamp 312 couples distractor rod 302 to first rotatablesegment 304. Similarly, another non-rotating yoke pin 339 is received incoaxial holes 316, 343 a, 343 b of T-clamp link 310, and tension clamp314 couples second rotatable segment 308 to T-clamp link 310.

Thus, when a desired orientation of distractor rod 302 or T-clamp link310 has been chosen, the fastener 332 may be tightened by threadablyengaging fastener 332 with insert nut 330 c, thereby decreasing thediameter of through hole 316 and decreasing the separation of extensions319 a, 319 b, so that articulation is arrested. Preferably, thearticulations about axes 318, 322 is simultaneously governed by thedegree of tightening of fastener 332; thus, for example, distractor bar302 either freely rotates about both axes 318, 322 or it is fixed inposition.

Swivel segment 306, shown in cross-section in FIG. 12J, includes a firstcylindrical end 344, a second cylindrical portion 345, and a thirdcircular end 346. The diameter of end 346 is larger than the diameter ofportion 345 which is larger than the diameter of end 344. In oneexemplary embodiment of first rotatable segment 304, a hole 348 isprovided, and is configured and dimensioned to receive end 344 andportion 345 of swivel segment 306, which may be fixed therein. End 344preferably is threadably received in hole 348. In an alternateembodiment, swivel segment 306 is rotatably retained or integrallyprovided in first rotatable segment 304.

Second rotatable segment 308 is shown in detail in FIGS. 13A to 13E.Main body 350 includes a hole 352 which receives a portion of swivelsegment 306. In one exemplary embodiment, third circular end 346 ofswivel segment 306 is disposed in close proximity to inner wall 354. Anupper slot 356 is provided, and is generally rectangular in shape. Inaddition, a hole 358 extends from slot wall 360 to outer wall 362. Afurther hole 364 is provided for use with tension clamp 314, similar topreviously described hole 340 in first rotatable segment 304. Holes 358,364 are disposed about axes 366, 368, respectively, and in one exemplaryembodiment these axes are substantially parallel to each other.

A cover 370 has a serrated portion 372, an arcuate recessed portion 374,a shoulder 376, and a hole 378. Cover 370 preferably may be about thesame size as upper slot 356 of second rotatable segment 308. Recessedportion 374 is configured and dimensioned to receive and retain thirdcircular end 346 of swivel segment 306, so that end 346 may rotatetherein. When cover 370 is inserted in upper slot 356, shoulder 376preferably abuts slot wall 360. Preferably, second cylindrical portion345 is serrated, so that serrations 372 of cover 370 engage portion 345.Moreover, an insert nut 330 d with a threaded hole is provided in a seatin hole 358, and when a fastener 332 is inserted in coaxial holes 378,358, so that the spherical lower portion of the head may be disposed ina spherical seat in hole 378, the fastener 332 threadably engages insertnut 330 d. Thus, swivel segment 306 in combination with first rotatablesegment 304 may freely rotate with respect to second rotatable segment308 when fastener 332 is loose, while rotation is arrested when fastener332 is tightened to draw serrated portion 372 of cover 370 and serratedsecond cylindrical portion 345 tightly together. The heads of fasteners332 each may include a spherical lower portion to mate with acorresponding spherical recessed portion in tension clamps 312, 314 andcover 370.

While various descriptions of the present invention are described above,it should be understood that the various features can be used singly orin any combination thereof. Therefore, this invention is not to belimited to only the specifically preferred embodiments depicted herein.

Further, it should be understood that variations and modificationswithin the spirit and scope of the invention may occur to those skilledin the art to which the invention pertains. For example, distractornuts, insert nuts, and lock screws may be formed integrally with thecomponents with which they are used. The insert nuts in some casesprovide threaded holes; in alternate embodiments, threading may beprovided integrally with a component to obviate the need for using athreaded insert nut. Other alternate embodiments of the presentinvention may use different configurations of the joints disclosedherein, such as several distractor joint assemblies which may be adaptedfor use with components other than the distractor bar. Also, althoughthe fixator of the present invention is described with both a distractorjoint assembly and a T-clamp joint assembly, other configurations offixators are within the scope of the present invention. One suchembodiment may include one or more distractor joint assemblies, but notinclude a T-clamp joint assembly. Further, although a distractor clampassembly and a T-clamp assembly are described, some fixators may haveonly one type of clamp assembly, or clamp assemblies other than the onesdescribed herein. In addition, the materials described for the presentinvention may be modified, such as by using other radiopaque materials.Moreover, although serrations have been described for use with mutuallyengaging elements and/or components, other suitably textured surfacesmay instead be used such as faceted surfaces. Accordingly, allmodifications readily attainable by one versed in the art from thedisclosure set forth herein are to be included as further embodiments ofthe present invention.

1. A bone fixator comprising: at least two clamping assemblies each forreceiving at least one bone fastener; a main body disposed between theclamping assemblies, the main body having a joint assembly comprising: amale segment having first and second ends and a projection extendingfrom the second end; a female segment having first and second ends, acavity disposed proximate the first end and configured and dimensionedto receive at least a portion of the projection, and an openingconnected to the cavity; and a cover piece configured and dimensioned tobe received in the opening and capable of being positioned in theopening so that a longitudinal axis of the cover piece is coextensivewith a longitudinal axis of the male segment, wherein when the malesegment is inserted in the female segment and the cover piece isdisposed in the opening, the cover piece resists removal of theprojection and the male segment is releasably rotatable with respect tothe female segment along a longitudinal axis of the main body and as thelongitudinal axis of the male segment is coextensive with a longitudinalaxis of the female segment.
 2. The bone fixator of claim 1, furthercomprising at least one tension clamp comprising: a body having aborehole extending therethrough along a borehole axis and a fastenerhole extending along a fastener axis transverse to the borehole axis,the body having an outer surface and an inner borehole surface; a slitextending along the borehole and across the fastener hole from the outersurface to the inner borehole surface, the slit defining opposed slitsurfaces having a separation width; and a fastener configured anddimensioned to be received in the fastener hole, wherein the size of theborehole is adjustable by changing the separation width of the opposedslit surfaces.
 3. The bone fixator of claim 1, further comprising adistractor body operatively associated with the male segment, wherein atleast one of the clamping assemblies is operatively associated with thedistractor body.
 4. The bone fixator of claim 3, wherein at least oneclamping assembly is translatable with respect to the distractor bodyand releasably lockable thereto.
 5. The bone fixator of claim 1, whereinat least one of the clamping assemblies comprises at least one of themale or female segments.
 6. A bone fixator comprising: at least twoclamping assemblies each for receiving at least one bone fastener; amain body disposed between the clamping assemblies, the main body havinga joint assembly comprising: a male segment having first and second endsand a projection extending from the second end; a female segment havingfirst and second ends, a cavity disposed proximate the first end andconfigured and dimensioned to receive at least a portion of theprojection, and an opening connected to the cavity; and a cover piececonfigured and dimensioned to be received in the opening, wherein whenthe male segment is inserted in the female segment and the cover pieceis disposed in the opening, the cover piece resists removal of theprojection and the male segment is releasable rotatable with respect tothe female segment along a longitudinal axis of the main body and as alongitudinal axis of the male segment is coextensive with a longitudinalaxis of the female segment, wherein the projection comprises a serratedcylindrical portion and the cover piece comprises a serrated arcuateinner surface, wherein the serrated cylindrical portion and the serratedarcuate inner surface are mutually positively lockable.
 7. The bonefixator of claim 6, wherein the female segment further comprises afastener hole and the cover piece further comprises a cover piece hole,the holes being coaxial when the cover piece is disposed in the opening.8. The bone fixator of claim 7, further comprising a fastener, whereinwhen the fastener is disposed in the coaxial fastener hole and coverpiece hole, the cover piece is securable to the female segment.
 9. Abone fixator comprising: at least two clamping assemblies each forreceiving at least one bone fastener; and at least one joint assemblycomprising: a first rotatable member comprising a first end, a secondend and a projection having a through hole with an axis, the projectiondisposed at the second end; a second rotatable member having a main bodycomprising a first end, a second end, a top surface, a bottom surface, acavity disposed proximate the first end, an opening in the top surface,the opening having a bottom surface, a cover configured and dimensionedto be received in the opening, and at least one fastening means, thecover being capable of being positioned in the opening so that alongitudinal axis of the cover is coextensive with a longitudinal axisof the first rotatable member; and a swivel member disposed between thefirst rotatable member and the second rotatable member, wherein thefirst rotatable member and the second rotatable member can rotate withrespect to one another while the longitudinal axis of the firstrotatable member remains coextensive with a longitudinal axis of thesecond rotatable member.
 10. The bone fixator of claim 9, wherein thefirst end of the first rotatable member further comprises a through holehaving an axis and wherein the axis of the through hole in theprojection and the axis of the through hole in the first end aresubstantially perpendicular to each other.
 11. The bone fixator of claim9, wherein the swivel member comprises: a first cylindrical end having adiameter; a second cylindrical end having a diameter; and a cylindricalportion disposed between the first and second cylindrical ends andhaving a diameter; wherein the diameter of the second cylindrical end isgreater than the diameter of the cylindrical portion, which is greaterthan the diameter of the first cylindrical end.
 12. The bone fixator ofclaim 9, wherein the cavity disposed proximate the first end of thesecond rotatable member is in communication with the opening in the topsurface of the second rotatable member.
 13. The bone fixator of claim 9,wherein at least one of the clamping assemblies comprises at least oneof the first or second rotatable members.
 14. A bone fixator comprising:at least two clamping assemblies each for receiving at least one bonefastener; and at least one joint assembly comprising: a first rotatablemember comprising a first end, a second end and a projection having athrough hole with an axis, the projection disposed at the second end; asecond rotatable member having a main body comprising a first end, asecond end, a top surface, a bottom surface, a cavity disposed proximatethe first end, an opening in the top surface, the opening having abottom surface, a cover configured and dimensioned to be received in theopening, and at least one fastening means, the cover being capable ofbeing positioned in the opening so that a longitudinal axis of the coveris coextensive with a longitudinal axis of the first rotatable member;and a swivel member disposed between the first rotatable member and thesecond rotatable member, wherein the first rotatable member and thesecond rotatable member can rotate with respect to one another while alongitudinal axis of the first rotatable member remains coextensive witha longitudinal axis of the second rotatable member, wherein the swivelmember comprises: a first cylindrical end having a diameter; a secondcylindrical end having a diameter; and a cylindrical portion disposedbetween the first and second cylindrical ends and having a diameter;wherein the diameter of the second cylindrical end is greater than thediameter of the cylindrical portion, which is greater than the diameterof the first cylindrical end, wherein the projection of the firstrotatable member is configured and dimensioned to receive the firstcylindrical end of the swivel member and the cavity of the secondrotatable member is configured and dimensioned to receive the secondcylindrical end of the swivel member.
 15. A bone fixator comprising: atleast two clamping assemblies each for receiving at least one bonefastener; and at least one joint assembly comprising: a first rotatablemember comprising a first end, a second end and a projection having athrough hole with an axis, the projection disposed at the second end; asecond rotatable member having a main body comprising a first end, asecond end, a top surface, a bottom surface, a cavity disposed proximatethe first end, an opening in the top surface, the opening having abottom surface, a cover configured and dimensioned to be received in theopening, and at least one fastening means, the cover being capable ofbeing positioned in the opening so that a longitudinal axis of the coveris coextensive with a longitudinal axis of the first rotatable member;and a swivel member disposed between the first rotatable member and thesecond rotatable member, wherein the first rotatable member and thesecond rotatable member can rotate with respect to one another while alongitudinal axis of the first rotatable member remains coextensive witha longitudinal axis of the second rotatable member, wherein the swivelmember comprises: a first cylindrical end having a diameter; a secondcylindrical end having a diameter; and a cylindrical portion disposedbetween the first and second cylindrical ends and having a diameter;wherein the diameter of the second cylindrical end is greater than thediameter of the cylindrical portion, which is greater than the diameterof the first cylindrical end, wherein the cylindrical portion isserrated.
 16. The bone fixator of claim 15, wherein the cover comprises:a serrated portion configured and dimensioned to engage the serrationsin the cylindrical portion of the swivel member; an arcuate recessedportion configured and dimensioned to receive the second end of theswivel member; a shoulder; and a hole; wherein the first rotatablemember in combination with the swivel member freely rotates with respectto the second rotatable member when the fastening means is loose; andwherein tightening of the fastening means draws the serrated portion ofthe cover and the serrations of the cylindrical portion together,thereby arresting rotation of the first rotatable member in combinationwith the swivel member with respect to the second rotatable member. 17.A bone fixator comprising: at least two clamping assemblies each forreceiving at least one bone fastener; and at least one joint assemblycomprising: a first rotatable member comprising a first end, a secondend and a projection having a through hole with an axis, the projectiondisposed at the second end; a second rotatable member having a main bodycomprising a first end, a second end, a top surface, a bottom surface, acavity disposed proximate the first end, an opening in the top surface,the opening having a bottom surface, a cover configured and dimensionedto be received in the opening, and at least one fastening means; and aswivel member disposed between the first rotatable member and the secondrotatable member, wherein the first rotatable member and the secondrotatable member can rotate with respect to one another while alongitudinal axis of the first rotatable member remains coextensive witha longitudinal axis of the second rotatable member, the bone fixatorfurther comprising a distractor body operatively associated with thefirst rotatable member, wherein at least one of the clamping assembliesis operatively associated with the distractor body.
 18. The bone fixatorof claim 17, wherein at least one clamping assembly is translatable withrespect to the distractor body and releasably lockable thereto.
 19. Abone fixator comprising: at least two clamping assemblies each forreceiving at least one bone fastener; and at least one joint assemblycomprising: a first rotatable member comprising a first end, a secondend and a projection having a through hole with an axis, the projectiondisposed at the second end; a second rotatable member having a main bodycomprising a first end, a second end, a top surface, a bottom surface, acavity disposed proximate the first end, an opening in the top surface,the opening having a bottom surface, a cover configured and dimensionedto be received in the opening, and at least one fastening means; and aswivel member disposed between the first rotatable member and the secondrotatable member, wherein the first rotatable member and the secondrotatable member can rotate with respect to one another while alongitudinal axis of the first rotatable member remains coextensive witha longitudinal axis of the second rotatable member, the bone fixatorfurther comprising at least one tension clamp comprising: a body havinga borehole extending therethrough along a borehole axis and a fastenerhole extending along a fastener axis transverse to the borehole axis,the body having an outer surface and an inner borehole surface; a slitextending along the borehole and across the fastener hole from the outersurface to the inner borehole surface, the slit defining opposed slitsurfaces having a separation width; and a fastener configured anddimensioned to be received in the fastener hole, wherein the size of theborehole is adjustable by changing the separation width of the opposedslit surfaces.
 20. A bone fixator comprising: at least two clampingassemblies each for receiving at least bone fastener; a main bodydisposed between the clamping assemblies, the main body having a jointassembly comprising: a male segment having first and second ends and aprojection extending from the second end; a female segment having firstand second ends, a cavity disposed proximate the first end andconfigured and dimensioned to receive at least a portion of theprojection, and an opening connected to the cavity; and a cover piececonfigured and dimensioned to be received in the opening and capable ofbeing positioned in the opening so that a longitudinal axis of the coverpiece is coextensive with a longitudinal axis of the male segment,wherein when the male segment is inserted in the female segment and thecover piece is disposed in the opening, the cover piece resists removalof the projection and the male segment is releasably rotatable withrespect to the female segment along a longitudinal axis of the main bodyand as a longitudinal axis of the male segment is coextensive with alongitudinal axis of the female segment; and at least one tension clampcomprising: a body having a borehole extending therethrough along aborehole axis and a fastener hole extending along a fastener axistransverse to the borehole axis, the body having an outer surface and aninner borehole surface; a slit extending along the borehole and acrossthe fastener hole from the outer surface to the inner borehole surface,the slit defining opposed slit surfaces having a separation width; and afastener configured and dimensioned to be received in the fastener hole;wherein the size of the borehole is adjustable by changing theseparation width of the opposed slit surfaces.